Energy Storage Devices Having Coated Passive Particles

ABSTRACT

The present invention provides various passive electronic components comprising a layer of coated particles, and methods for producing and using the same. Some of the passive electronic components of the invention include, but are not limited to conductors, resistors, current collectors, capacitors, piezoelectronic devices, inductors and transformers. The present invention also provides energy storage devices and electrode layers for such energy storage devices having passive, electrically-conductive particles coated with one or more thin film materials.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.16/129,642, filed Sep. 12, 2018, which is a Continuation-in-Part of U.S.patent application Ser. No. 15/301,102, filed Sep. 30, 2016, which isthe National Phase of International Patent Application No.PCT/US2015/023550, filed Mar. 31, 2015, published on Oct. 8, 2015 as WO2015/153584, which claims priority to U.S. Provisional Application No.61/973,352, filed Apr. 1, 2014. The contents of these applications areherein incorporated by reference in their entirety.

FEDERAL FUNDING STATEMENT

This Invention was made with government support under Contract No.DE-SC0010239 awarded by the Department of Energy. The Government hascertain rights in this invention.

FIELD OF THE INVENTION

The present invention relates to various passive electronic componentscomprising a layer of coated nanoparticles, and methods for producingand using the same. In particular, the present invention relates toenergy storage devices having the passive components.

BACKGROUND OF THE INVENTION

The incorporation of particles from millimeter-scale down to nanometersin size is ubiquitous in end-use products produced in industrial-scalequantities. A significant percentage of the particles used across allindustries require that the surfaces be coated with a shell, layer,film, or other coating, ranging from sub-nanometer to hundreds ofmicrometers in thickness. For a variety of reasons, each sector orindustry has determined that the incorporation of coated particles intothe end-use product provides enough value, e.g., in the form of enhancedperformance of the product, that the cost associated with each coatingprocess is justified. Energy storage is one application where nanoscalecoatings can significantly improve the uniformity and compatibility ofsurfaces, allowing for preferential transfer of beneficial ions orelectrons across interfaces, while reducing the propensity fordetrimental or corrosion promoting species from degrading or otherwisealtering these interfaces.

The performance of passive electronic components such as capacitortechnologies, including single-layer or multilayered ceramic capacitors(MLCC), electrolytic capacitors, polymer film capacitors, or emergingultracapacitor and/or supercapacitor systems, relies on the quality ofcontrol across interfaces, which in turn defines the specification forcapacitance, dielectric strength, breakdown voltage, dielectric loss,etc. Mechanisms to tailor and optimize all surfaces of all materialscontained within the system leads to better control, definition,functionality or other specification of performance of any feature ofeach system.

Ceramic capacitors (bulk ceramic and MLCCs) have existed for quite sometime, and the state of the art has progressively advanced to higherenergy density, power density, lifetime/durability, and similaradvances, all while occupying a decreasing footprint that trends withsmaller sizes of integrated circuit technologies. Barium titanate(BaTiO₃) is a commonly used dielectric material. Extensive work on thismaterial has demonstrated that tailored bulk content (e.g., dopants,protonation, etc.) or utilization of surface coatings (e.g., Al₂O₃,SiO₂, etc.) can be used to achieve higher breakdown voltages thanuntreated materials. Constantino et al. (U.S. Patent ApplicationPublication No. 2001/0048969) discusses Al₂O₃-coated or SiO₂-coatedsub-micron BaTiO₃ particles that are exemplary of these additionalperformance features. Many other tactics have been used to modifydielectric materials to achieve improved device properties.

Methods of producing compositionally-tailored ceramic/dielectric layersthemselves using additive, layer-by-layer controlled techniques, eventhose as precise as Atomic Layer Epitaxy or Atomic Layer Deposition asdescribed by Suntola et al. (U.S. Pat. No. 4,058,430), have beendeployed to achieve similar effects (see, for example, Ahn, et al., U.S.Patent Application Publication No. 2011/0275163). In addition,techniques that cast or otherwise form a bulk layer consisting of aplurality of compositionally-tailored coated dielectric particles havealso been described. See, for example, Constantino et al. in U.S. PatentApplication Publication No. 2001/0048969. Coating processes forparticles as precise as Atomic Layer Deposition is described by Lakomaa,et al. in the seminal demonstration of ALD coated particles: “Atomiclayer growth of TiO₂ on silica”, Applied Surface Science 60/61 (1992)742-748.

Several years after the seminal publication of conformal metal oxidecoatings on microfine powders (produced using sequential self-limitinggas phase reactions that occurred homogeneously on the surfaces ofparticles in a fixed bed of particles enclosed in a single batchreactor), additional patents have been issued pertaining to ALD andnon-ALD techniques for producing high quality coatings on particles,including nanoparticles. As examples included herein by reference,Krause et al. (EP 0865819) discuss methods of encapsulating particlesusing fluidized beds; Cansell et al. (U.S. Pat. No. 6,592,938) discussmethods of coating particles using organometallic precursors that areindividually known to undergo self-limiting reactions under traditionalALD conditions. Cansell further discusses (see U.S. Pat. No. 7,521,086)as to how the latter coating technique could similarly be utilized forthe production of a metal oxide encapsulated BaTiO₃.

As described by King et al. (US 20110236575), vapor deposition processesare usually operated batch-wise in reaction vessels such as fluidizedbed reactors, rotary reactors and V-blenders, amongst others. Batchprocesses have significant inefficiencies when operated at large scale.One of the disadvantages of batch processes is that the reactorthroughput is a function of the total particle mass or volume loadedinto a certain sized vessel for a given process, the total process time(up-time), and the total time between processes (down-time) to load,unload, clean, prepare, etc. In addition, batch processes incur largedown-times because at the end of each batch the finished product must beremoved from the reaction equipment and fresh starting materials must becharged to the equipment before the subsequent batch can be produced.Equipment failures and maintenance add to this downtime in batchprocesses.

Moreover, relatively speaking, batch process equipment tends to be verylarge and expensive. The need to operate these processes under vacuumadds greatly to equipment costs, especially as equipment size increases.Because of this, equipment costs for batch processes tend to increasefaster than operating capacity.

Another problem that occurs as the process equipment becomes larger isthat it becomes more difficult to maintain uniform reaction conditionsthroughout the vessel. For example, temperatures can vary considerablywithin a large reaction vessel. It is also difficult to adequatelyfluidize a large mass of particles, specifically nanoparticles. Issuessuch as these can lead to inconsistencies and defects in the coatedproduct.

In vapor deposition processes such as ALD and Molecular Layer Deposition(MLD), the particles are contacted with two or more different reactantsin a sequential manner. This represents yet another problem for a batchoperation. For a traditional batch process, all cycles are performedsequentially in a single reaction vessel. The batch particle ALD processincurs additional down-time due to more frequent periodic cleaningrequirements, and the reaction vessels cannot be used for multiple filmtypes when cross-contamination could be problematic. In addition, thetwo sequential self-limiting reactions may occur at differenttemperatures, requiring heating or cooling of the reactor between cyclesteps in order to accommodate each step.

The throughput for a batch process can be increased either by buildinglarger reaction vessels and/or operating identical reaction vessels inparallel. The capital cost to counteract this down-time from athroughput perspective is to build a larger reaction vessel. With largervessels, localized process conditions, including internal bed heating,pressure gradients, mechanical agitation to break up nanoparticleaggregates, and diffusion limitations amongst others, become moredifficult to control.

Furthermore, there is a practical maximum reaction vessel size whenperforming ALD processes on fine and ultra-fine particles, which limitsthe throughput for a single batch reactor operating continually. Ingeneral, the time duration for the process of producing a given amountof coated materials equals the up-time plus down-time. There is also apractical maximum allowable in capital expense to fabricate anALD-coated particle production facility, which effectively limits thenumber of batch reactors that can operate identical processes inparallel. With these and other constraints, there are practicalthroughput limitations that prohibit the integration of some particleALD processes at the industrial scale.

King et al. (U.S. Patent Application Publication No. 2011/0236575)discusses a high-rate “Spatial ALD” manufacturing process and apparatusfor coating particles in semi-continuous fashion using an array ofisolated vessels with counter-current gas-solids transport. As describedin King et al., one example where a semi-continuous coated particlemanufacturing process is desirable is a facility that utilizes particleALD to produce fine or ultra-fine passivated titanium dioxide particlesused as pigments in paints, plastics, paper, etc. Another example is afacility that utilizes particle ALD to produce coated fine or ultra-fineparticles for cathodes, anodes, dielectrics, metals, polymers,semiconductors and other ceramics for integration into power systemsdevices including, but not limited to, batteries, capacitors, varistors,thyristors, inverters, transistors, light emitting diodes and phosphors,photovoltaic, and thermoelectric devices. Particle ALD produced powdersfor the pigment and power systems industries can significantly improvethe performance of the end-use products, which can be cost competitiveif produced at high annual throughputs.

Van Ommen et al. (U.S. Patent Application Publication No. 20120009343)discusses another high-rate “Spatial ALD” process and apparatus to coatparticles in a fully continuous co-current gas-solids transport scheme.Each of these methods has its own ascribed operating cost. These methodsare suitable for the manufacture of particular coated particles. Inaddition, each of these methods is believed to be superior andeconomically more viable to traditional batch (or “temporal”) ALDcoating methods. Fotou et al. (Sequential Gas-Phase Formation of Al₂O₃and SiO₂ Layers on Aerosol-Made TiO₂ Particles” Advanced Materials(1997), 9, No. 5, 420-423) discuss methods of producing nanocoatings onsubmicron particles by exposing reactive precursors to the surfaces ofparticles using continuous-flow Chemical Vapor Deposition techniques.However, the consistency, uniformity and thickness do not lendthemselves easily to less than 5 nm coatings on submicron-sizedparticles.

It is expected that a thin film coating (e.g., 5 nm or less) onnanoparticles that are used in passive electronic components willprovide a significant protection from degradation and/or oxidation ofnanoparticles while maintaining substantially all of its electronicfunction.

Accordingly, there is a need for thin film coated nanoparticles andmethods for producing and using the same in passive electroniccomponents.

SUMMARY OF THE INVENTION

Some aspects of the invention provide a passive electronics componentcomprising nanoparticles that are coated with a thin film of material.The thin film coating can be an oxidation-resistant material or areliability-improving material. As used herein, the term“reliability-improving materials” refers to materials that can improvethe performance and/or the life span or mean time to failure of thepassive electronics component compared to the same passive electronicscomponent in the absence of the thin film coating. In one particularinstance, the reliability-improving materials increase the performanceof the passive electronics component by at least 10%, typically by atleast 25%, and often by at least 100%. compared to the same passiveelectronics component in the absence of the thin film coating. Inanother instance, the reliability-improving materials increase the meantime to failure of the passive electronics component by at least 20%,typically by at least 50%, and often by at least 200% relative to thesame passive electronics component in the absence of the thin filmcoating.

As used herein, the terms “same passive electronics component in theabsence of the thin film coating” and “similar passive electronicscomponents in the absence of the thin film coating” are usedinterchangeably herein and refer to the electronics component that isproduced using the same material and same process except for the absenceof the thin film coating.

In one aspect, disclosed herein is an electrode layer for an energystorage device which includes active and passive components, wherein theelectrode layer includes passive, electrically-conductive particlescoated with a thin film of protective material. In at least oneembodiment, the function of the electrode layer may be substantially thesame to a similar electrode layer of passive, electrically-conductiveparticles in the absence of the protective material.

In at least one embodiment, the passive, electrically-conductiveparticles are metallic and/or polymeric. In at least one embodiment, themetallic and/or polymeric particles include aluminum, platinum, silver,gold, titanium, copper, zinc, chromium, nickel, iron, molybdenum,tungsten, ruthenium, palladium, indium, PtNi, FeCrAlY, AgPd, nichrome,other conductive steels, PEDOT, other conductive polymers, orcombinations thereof. In at least one embodiment, the passive,electrically-conductive particles include carbons, carbon black,acetylene black, activated carbon, carbon nanotubes, carbon fibers,vapor grown carbon fibers, carbon nanoribbons, graphite, graphene,diamond or diamond like carbon, and combinations thereof. In at leastone embodiment, the energy storage device includes a battery, asingle-layer capacitor, multi-layer capacitor or an ultracapacitor.

In at least one embodiment, the electrode layer is produced from acasting, printing or spraying process. In at least one embodiment, theelectrically-conductive particles have a median particle size of 3,000nanometers or less. In at least one embodiment, the thin film ofprotective material has a thickness of about 20 nanometers or less.

Exemplary thin film protective material include, but not limited to,aluminum oxide, hafnium oxide, zirconium oxide, tantalum oxide, niobiumoxide, lithium oxide, silicon oxide, calcium oxide, magnesium oxide,boron oxide, aluminum phosphate, titanium phosphate, lithium phosphate,calcium phosphate, aluminum nitride, gallium nitride, boron nitride,boron carbide, zinc oxide, titanium oxide, cerium oxide, vanadium oxide,barium oxide, bismuth oxide, ruthenium oxide, indium oxide, tin oxide,lanthanum oxide, titanium nitride, tantalum nitride, silicon carbide,and binary, ternary or quaternary combinations thereof. In at least oneembodiment, the thin film of protective material is produced usingatomic layer deposition, molecular layer deposition, chemical vapordeposition, or combinations thereof.

In at least one embodiment, the lifetime of an electrode layercomprising thin film protected electrically-conductive particles is atleast 10% more than an electrode layer with uncoatedelectrically-conductive particles. In at least one embodiment, the ratecapability of an electrode layer comprising thin film protectedelectrically-conductive particles is at least 10% more than an electrodelayer with uncoated electrically-conductive particles.

In yet another aspect, disclosed herein is an energy storage devicecomprising an electrode layer having passive, electrically-conductiveparticles, wherein the electrically-conductive particles comprise one ormore of copper, nickel or aluminum, and wherein theelectrically-conductive particles are coated with one or more thin filmprotective materials. In at least one embodiment, the coating on theelectrically-conductive particles is produced using an atomic layerdeposition or a molecular layer deposition process. The energy storagedevice may have a resistivity value less than 10,000 μΩ-cm, producedusing atomic layer deposition or molecular layer deposition.

In one particular aspect of the invention, the passive electronicscomponent comprises an electrode layer of electric conductingnanoparticles. The nanoparticles of the invention are coated with a thinfilm of oxidation-resistant material. The thin film ofoxidation-resistant material prevents oxidation of the nanoparticleswhile maintaining the function of the electrode layer substantially thesame as that of a similar electrode layer of electric conductingnanoparticles in the absence of said thin film of oxidation-resistantmaterial. As used herein, the term “similar electrode layer” refers toan electrode layer that is produced in identical conditions except forthe absence of the thin film of oxidation-resistant material. The term“nanoparticles” refers to particles having average or median particlesize of 1000 nm or less, typically 500 nm or less, often 400 nm or less,and most often 250 nm or less. Alternative, the term “nanoparticles”refers to particles in which 80% or more, typically 90% or more andoften 95% or more of the particles have the particle size of 1000 nm orless, typically 800 nm or less, and often 600 nm or less. As usedherein, the term “thin film” refers to a film or a coating of a materialhaving mean or median thickness of about 20 nm or less, typically 10 nmor less, often 5 nm or less, and most often 3 nm or less. Alternatively,the term “thin film” refers to a film of from about 2 to about 6 nm inthickness. Still alternatively, the term “thin film” refers to amono-atomic or molecular layer of coating material. Often, the term“thin film” refers to the thickness of a coating material achieved usingthe process disclosed in a commonly assigned U.S. patent applicationSer. No. 13/069,452, entitled “Semi-Continuous Vapor Deposition ProcessFor The Manufacture of Coated Particles.” In general, the thin film isformed by an atomic layer deposition process, which can be carried outin a batch mode, semi-continuous mode, continuous mode, or a combinationthereof. It should be appreciated that the thin film can also be formedusing any of the methods known to one skilled in the art.

In some embodiments, the thin film of oxidation-resistant materialprovides no significant additional resistivity to said nanoparticles.The term “no significant additional resistivity” refers to a resistivityof a coated nanoparticle, which first has its native oxide removed priorto coating, whose resistivity differs from the resistivity of uncoatednanoparticle of same composition, without the native oxide beingremoved, by no more than about 20%, typically no more than about 10%,and often no more than about 5%.

Yet in other embodiments, the thin film of oxidation-resistant materialdoes not significantly affect the sintering of said nanoparticles. Asused herein, the term “sintering” refers to atomistic diffusion betweennanoparticle and the thin film or atomistic diffusion betweennanoparticles. Also as used herein, the term “does not significantlyaffect the sintering of said nanoparticles” means the amount ofsintering or the sintering temperature in the presence of the thin filmcoating is substantially similar to the amount of sintering or thesintering temperature of the same nanoparticles in the absence of a thinfilm coating. Generally, the amount of nanoparticle sintering in thepresence of the thin film coating is no more than 15%, typically no morethan 10%, and often no more than 5% different compared to the amount ofnanoparticle sintering in the absence of the thin film coating.Alternatively, the sintering temperature in the presence of the thinfilm coating is within 50° C., typically within 30° C., and often within20° C. of the nanoparticle sintering temperature in the absence of thethin film coating.

Still in other embodiments, the thin film of oxidation-resistantmaterial comprises a thin film of wide bandgap material. As used herein,the term “wide bandgap material” refers to materials with electronicband gaps significantly larger than 1.5 electron volt (eV), typicallylarger than 3.0 eV, and often larger than 5.0 eV. In some instances, thewide bandgap material comprises a material selected from the groupconsisting of aluminum oxide, hafnium oxide, zirconium oxide, tantalumoxide, niobium oxide, lithium oxide, silicon oxide, calcium oxide,magnesium oxide, boron oxide, aluminum phosphate, titanium phosphate,lithium phosphate, calcium phosphate, aluminum nitride, gallium nitride,boron nitride, boron carbide, and a combination thereof. Still in otherinstances, the thickness of the thin film coating of wide bandgapmaterial is 8 nm or less, typically 5.5 nm or less, and often 3.5 nm orless.

In other embodiments, the thin film of oxidation-resistant materialcomprises a thin film of semiconducting or conducting material.Exemplary semiconducting or conducting materials that are suitable forthe present invention include, but are not limited to, zinc oxide,titanium oxide, cerium oxide, vanadium oxide, barium oxide, bismuthoxide, ruthenium oxide, indium oxide, tin oxide, lanthanum oxide,titanium nitride, tantalum nitride, silicon carbide, and ternary orquaternary combinations that include these and other analogousmaterials. Exemplary conducting materials that are useful in the presentinvention include, but are not limited to, metals (such as platinum,silver, gold, titanium, copper, zinc, chromium, nickel, iron,molybdenum, tungsten, ruthenium, palladium, indium, and tin), alloys orintermetallics (such as PtNi, FeCrAlY, AgPd, nichrome, and otherconductive steels) and other electric conducting materials such as thosecontaining carbon (including carbons, carbon black, acetylene black,activated carbon, carbon nanotubes, carbon fibers, vapor grown carbonfibers, carbon nanoribbons, graphite, graphene, diamond and diamond likecarbon, and PEDOT and other conductive polymers).

In other embodiments, suitable thin film of protective material mayinclude one or more materials selected from aluminum oxide, hafniumoxide, zirconium oxide, tantalum oxide, niobium oxide, lithium oxide,silicon oxide, calcium oxide, magnesium oxide, boron oxide, aluminumphosphate, titanium phosphate, lithium phosphate, calcium phosphate,aluminum nitride, gallium nitride, boron nitride, boron carbide, zincoxide, titanium oxide, cerium oxide, vanadium oxide, barium oxide,bismuth oxide, ruthenium oxide, indium oxide, tin oxide, lanthanumoxide, titanium nitride, tantalum nitride, silicon carbide, or the like,and binary, ternary or quaternary combinations thereof.

In one particular embodiment, the resistivity of the thin film ofoxidation-resistant material or the coating is 50,000 μΩ-cm or less,typically 5,000 μΩ-cm or less, and often 500 μΩ-cm or less. In at leastone embodiment, the electrically-conductive coatings may have aresistivity value less than 10,000 μΩ-cm.

Yet in other embodiments, the thin film of oxidation-resistant materialcomprises a dopant material. Exemplary dopant materials that are usefulin the invention include, but are not limited to, +5 valence materialsinto +4 valence materials (such as tantalum oxide doped into titaniumoxide), +3 valence materials into +2 valence materials (such as aluminumoxide doped into zinc oxide), and commonly known doped transparentconductive oxides (such as fluorine-doped tin oxide). Typically, thedopant material increases the conductivity of the thin film ofoxidation-resistant material by at least 20%, often by at least 50% andmost often by at least 100%.

Still in other embodiments, a thermal oxidation onset temperature of thenanoparticles with the thin film coating is at least 10° C., typicallyat least 25° C., and often at least 100° C. higher than the samenanoparticles in the absence of said thin film of oxidation-resistantmaterial.

Yet still in other embodiments, the average particle size of saidnanoparticles is 1,000 nm or less, typically 800 nm or less, and often500 nm or less.

Depending on a particular application, the passive electronics componentcan comprise a plurality of said electrode layers.

Another aspect of the invention provides a passive electronics componentcomprising a dielectric or piezoelectric layer of correspondingnanoparticles that are coated with a thin film of areliability-improving material. In this aspect of the invention, thenanoparticles are dielectric or piezoelectric nanoparticles. Exemplarydielectric or piezoelectric materials that are useful in the presentinvention include nanoparticles composed of materials including, but arenot limited to, barium titanate, strontium titanate, barium strontiumtitanate, barium niobate, strontium niobate, barium strontium niobate,sodium niobate, potassium niobate, sodium potassium niobate, titania,zirconia, lead zirconate, lead zirconate titanate, calcium coppertitanate, bismuth scandium oxide, bismuth zinc oxide, bismuth titanate,bismuth zinc titanate, zinc oxide, and zinc titanate.

In some embodiments, the reliability-improving material comprises SiO₂,ZrO₂, B₂O₃, Bi₂O₃, Li₂O, or a mixture thereof.

Still in other embodiment, the thin film coating reduces thedensification onset temperature of said nanoparticles. As used herein,the term “densification” means atomistic diffusion between or within thethin films, and/or interactions with additional densification aids (suchas glass or glass-forming powders) present in the system, as relevant.Also as used herein, the “densification onset temperature” means thetemperature at which nanoparticles coated with thin films begin todensify and reduce the void space present between a plurality of saidnanoparticles. The densification temperature of nanoparticles in theabsence of a thin film coating is the same as the sintering temperatureof the nanoparticles. Alternatively, the thin film coating serves as asolid precursor to liquid phase sintering of the nanoparticles, attemperatures substantially lower than the traditional sinteringtemperature of said nanoparticles. In general, the densificationtemperature of the nanoparticles is at least 25° C. lower, typically byat least 50° C. lower, and often by at least 100° C. lower than thesintering temperature of the same nanoparticles in the absence of thethin film coating.

In one particular embodiment, said nanoparticles comprise bariumtitanate, and said reliability-improving material comprises an oxide ofa metal comprising bismuth, zinc, titanium, scandium, or a mixturethereof. In some instances within this embodiment, saidreliability-improving material comprises zinc titanium oxide, bismuthzinc titanium oxide or bismuth scandium oxide.

In another embodiment, said nanoparticles comprise an alkali niobateperovskite, and said reliability-improving material comprises an oxideof a metal selected from the group consisting of tantalum, sodium,potassium, or a mixture thereof. In some instances within thisembodiment, said reliability-improving material comprises an alkalitantalate.

Yet in another particular embodiment, said reliability-improvingmaterial increases the mean time to failure by at least 10% relative tothe same passive electronics component in the absence of said thin filmof reliability-improving material.

Still in another particular embodiment, said thin film ofreliability-improving material reduces the average grain size of saidnanoparticles by at least 20 nm, typically by at least 50 nm, and oftenby at least 100 nm when fired into fully-dense parts.

As stated above, the thin film coating in some embodiments is producedat least in part using an atomic layer deposition or molecular layerdeposition process.

The scope of the invention also includes a passive electronics componentcomprising a plurality of said dielectric or piezoelectric layers.

Still another aspect of the invention provides a passive electronicscomponent comprising a dielectric and/or piezoelectric layer describedherein in combination with an electrode layer comprising electricconducting nanoparticles described herein. That is said nanoparticles ofsaid dielectric and/or piezoelectric layer are coated with a thin filmof a reliability-improving material and/or said electric conductingnanoparticles are coated with a thin film of oxidation-resistantmaterial.

Other aspects of the invention include an electronic device comprising apassive electronics component disclosed herein such as one or moreelectrode layer(s), dielectric layer(s), and/or piezoelectric layer(s).

One specific aspect of the invention provides a capacitor comprising athin film coated nanoparticles, wherein said thin film coatednanoparticles comprise an electric conducting nanoparticles that arecoated with a thin film of an oxidation-resistant material, and whereinsaid thin film prevents oxidation and sintering of but substantiallymaintains the electric conductivity property of said nanoparticles. Insome embodiments, said oxidation-resistant material comprises a widebandgap material. In some embodiments, said capacitor is a multilayeredceramic capacitor or MLCC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 —A transmission electron microscope (TEM) image of an exemplaryset of coated electrode-grade nickel nanoparticles with limited (˜5-10%)agglomeration. Particles ranged from ˜50 nm to ˜600 nm in this sample.

FIG. 2 —A magnified TEM image of the lower left portion of FIG. 1 ,showing coated particles that had agglomerated during the ALD coatingprocess using a batch fluidized bed reactor.

FIG. 3 —A magnified TEM image from the upper right portion of FIG. 1 ,showing coated particles that have necked together during the ALDcoating process using a batch fluidized bed reactor.

FIG. 4 —A high resolution TEM image of an exemplary ˜7 nm coating on anelectrode-grade nickel nanoparticle.

FIG. 5 —Thermal gravimetric analysis (TGA) thermal stability testing ofuncoated and coated electrode-grade nickel nanoparticles in air. Theweight was measured continuously while the temperature was increased ata 10° C./min rate. The uncoated material began to increase in weight,which is indicative of the onset of nickel oxidation, at 300° C.; thecoated material began to increase in weight at 700° C.

FIG. 6 —Thermal stability testing of uncoated and coated electrode-gradenickel nanoparticles at 300° C. for 12 hours, designed to mimic a binderburn-out process in air. The uncoated nickel nanopowder originally had0.1% NiO by weight, and oxidized to 16.6% NiO after the 12 hour dwellperiod. A sub-critical ALD coating thickness was used for the test, andreduced the amount of oxidation to 10.5%. The optimal coating thicknessidentified, which was twice as thick as the sub-critical ALD coatingthickness, effectively prevented all oxidation while allowing a binderburn-out process to occur at 300° C. in air rather than a conventionaltemperature of 270° C. in air.

FIG. 7 —Dielectric constant and loss (tan delta) measurements for alkaliniobate-nickel nanopowder co-fired capacitors produced with uncoated andcoated nickel nanopowder over a range of co-firing oxygen partialpressures. Nearly independent of oxygen partial pressures, the thin filmcoated nickel nanoparticles demonstrated ability for repeatabledielectric constant with ultra-low dielectric loss, without modifyingthe dielectric powders themselves. This invention can ultimately allowfor fast co-firing steps to be carried out in air, and allow thin filmcoated nickel or copper nanoparticles to supplant platinum andsilver-palladium used in air firing steps today. This test also showedthat even in samples with limited agglomeration due to the coatingprocess, the performance of mildly agglomerated thin film coated nickelnanoparticles remains suitable for electrode applications.

FIG. 8 —Dielectric constant and loss (tan delta) measurements for alkaliniobate-nickel nanopowder co-fired capacitors produced with uncoated andcoated nickel nanopowder over a range of co-firing oxygen partialpressures; raw data from FIG. 7 .

FIG. 9 —Comparison of XRD data for Ni and NiO for coated and uncoated NiPowders Fired in Air in an Elevator Kiln showing negligible NiO in theALD coated case. Images of Nickel ink samples after firing @ 800° C./3min (inset) are shown, with the outline color matching the colors on theXRD spectra legend. This data suggests that ALD coatings are much morerobust to thermal shock than originally anticipated. Those skilled inthe art have attributed the oxidation of nanocoated metal powders tofilm cracking allowing oxygen ingress, when viewing TGA data shown inFIG. 5 at a temperature ramp rate of 10° C./min; however an unexpectedlygreater thermal stability has been demonstrated for this ˜250° C./minthermal shock. The cooling time was substantial enough that the materialremained above 300° C. for long enough that additional oxidation wouldhave been rampant for grossly cracked films, and this was not the case.

DETAILED DESCRIPTION OF THE INVENTION

Electronic devices have become ubiquitous in today's society. As modernelectronic devices have become smaller, their components have alsobecome smaller. In fact, some components of modern electronic devicesare micro-scales. As these electronic components become smaller, theyare more susceptible to degradation or oxidation, which significantlyreduces the life of modern electronic devices. Electronic devicescontain both active and passive electronic components. The term “passiveelectronic components” refers to components of electronic devices thatcan't introduce net energy into the circuit. Exemplary passiveelectronic components include, but are not limited to, two-terminalcomponents such as resistors, capacitors, inductors, and transformers.In general, passive electronic components can't rely on a source ofpower, except for what is typically available from the circuit they areconnected to. Thus, passive electronic components can't amplify (e.g.,increase the power of a signal), but they may increase a voltage orcurrent (e.g., as is done by a transformer or resonant circuit).

While present invention relates to a thin film coated nanoparticles thatare used in various passive electronic components, for the sake ofbrevity and clarity the present invention will now be described inreference to capacitors. However, it should be appreciated that thescope of the invention includes thin film coated nanoparticles that areused in other passive electronic components such as resistors,inductors, and transformers. Moreover, methods disclosed herein can beused to produce such other passive electronic components. As mentionedhereinabove, energy storage device is an electronic device whichbenefits from such passive electronic components which include thin filmcoated nanoparticles or particles up to the size of the active materialparticles, or sometimes sized appropriately to fit between and/or withinthe void spaces amongst loosely or tightly packed active materialparticles. Examples of such energy storage devices includeelectrochemical systems such as batteries, capacitors (e.g.,single-layer capacitors, multi-layer capacitors and ultracapacitors),fuel cells, electrochemical capacitors, and combinations thereofincluding hybrid capacitors, lithium-ion capacitors and lithium-airbatteries. Examples of batteries include lead-acid, nickel metalhydride, alkaline, lithium metal, lithium ion, solid state electrolytebatteries, lithium polymer, sodium ion, magnesium ion, aluminum ion,lithium sulfur, sodium silicon, and similar systems known to one ofordinary skill in the art. Lithium ion batteries are one such example ofan energy storage device, which are used as portable energy source formany electronic devices due to their high power and energy density aswell as long shelf life. There is an industrial interest in increasingthe energy density of lithium ion batteries, as a way to reduce the costper energy unit of these batteries, to increase the consumer adoption ofelectric devices, including electric vehicles and portable electronics.

Today, MLCCs are most efficiently manufactured through the casting ofalternating layers of inks/pastes consisting of electrode powders anddielectric powders, stacked in direct contact with one another, andafter which binder burn-out and co-firing (e.g., sintering) steps areexecuted on assembled systems. Exemplary processing techniques aredescribed by Imanaka (“Multilayered Low Temperature Co-fired CeramicsTechnology”, Springer, 2005) and by Nakano et al. (U.S. Pat. No.7,595,974), which are incorporated herein by reference in theirentirety.

There is an industry need to supplant the use of silver, platinum,palladium, and other costly precious metals used in electrodeinks/pastes with base metals having one or more protective oxidationbarrier coatings. Adopting suitable methods of supplanting expensivematerials for low-cost base metals that achieve the same level ofapplication functionality will significantly reduce the cost of MLCCsand other advanced power electronics devices. Hakim et al. (“Synthesisof oxidation-resistant metal nanoparticles via atomic layer deposition”Nanotechnology 29 (2007) 345603-345609) discusses how ALD can be used toencapsulate base metal particles, and extend their oxidation onsettemperature by hundreds of degrees Celsius. Furthermore, ultrafine basemetal powders can be produced via metal oxalate decomposition asdescribed by Dunmead et al. (U.S. Pat. No. 6,689,191). Those skilled inthe art have claimed that the oxidation onset temperature is driven byfilm cracking, however the present thin film coated nanoparticles can bethermally treated above this oxidation onset temperature duringfast-firing steps without substantial oxidation as would be anticipatedfrom films that crack at the oxidation onset temperature as measuredusing slow heating rates.

It is unexpected, however, that when producing insulator-coatedelectrode powders using ALD, that these composite particles (e.g.,BaTiO₃—Ni MLCCs with co-fired inner electrodes) can function as well aspristine base metal electrode powders used today. Especially in light ofU.S. Pat. No. 7,132,697, issued to Weimer et al. (the “Weimer et al.Patent”), discussing that ALD coated metal particles of 10 nm to 500 μmin diameter, with insulating coatings of 0.25 nm-500 nm in thickness,demonstrated non-linear resistivity with respect to film thickness. Thispatent implicitly appears to teach that metal particles coated withinsulating metal oxide coatings deposited using ALD cannot serve as adrop-in replacement to uncoated particles in many other passivecomponent applications such as capacitors and conductors.

In contrast to these teachings, the present inventors have discoveredthat the incorporation of 2-5 nm Al₂O₃ ALD coated submicron metallic Niparticles (600 nm and smaller) results in no significant additionalresistivity even when operating at voltages below the accepted breakdownstrength of bulk aluminum oxide. In some embodiments, metallic nickelparticles are subjected to native oxide removal pretreatments prior tocoating. The resulting ALD-coated metallic nickel particles can be usedto either fully or partially supplant uncoated Ni particles (or thecorresponding Ag, Pt and other common electrode materials). Similarly,ALD-coated metallic copper particles can be used to either fully orpartially supplant uncoated Cu particles (or the corresponding Ag, Ptand other common electrode materials). Accordingly, some aspects of theinvention provide a single-layer ceramic capacitor and/or MLCCs thatyields no significant additional resistivity due to the coatingsrelative to the base metal itself. As used herein, the term “nosignificant additional resistivity” refers to a resistivity of anALD-coated base metal nanoparticle, which first has its native oxideremoved prior to coating, whose resistivity differs from the resistivityof uncoated base metal nanoparticle of same composition with its nativeoxide intact, by no more than about 20%, typically no more than about10%, and often no more than about 5%. In some embodiments, the thin filmof oxidation-resistant material provides no significant additionalresistivity to said nanoparticles. Moreover, it has been discovered bythe present inventors that a wide variety of core materials or particlessuch as nanoparticles that can be used in passive electronic componentscan be coated with a thin film of protective material. As used herein,the term “nanoparticles” refers to particles having average or medianparticle size of 1,000 nm or less, typically 500 nm or less, often 400nm or less, and most often 250 nm or less. Alternative, the term“nanoparticles” refers to particles in which 80% or more, typically 90%or more and often 95% or more of the particles have the particle size of1,000 nm or less, typically 800 nm or less, and often 600 nm or less. Asused herein, the term “thin film” refers to a film or a coating of amaterial having mean or median thickness of about 20 nm or less,typically 10 nm or less, often 5 nm or less, and most often 3 nm orless. The term “base material” refers to the core material ornanoparticles of the invention. The term “coating” or “shell” issometimes used to describe a thin film of material that covers thenanoparticles or the core material. It should be appreciated that thenanoparticle material and the thin film of coating are typicallycomposed of different materials. As described in the Weimer et al.patent, suitable conductive core materials have resistivities in therange from about 10⁻¹ to about 10⁻⁶ ohms/cm. Examples of such materialsinclude metals such as copper, aluminum, nickel (including carbonylnickel) molybdenum, silver, gold, zinc, cadmium, iron, tin, berylliumand lead; alloys of one or more of the foregoing metals, steel, bronze,brass and Mu-metal; various carbides such as titanium carbide, columbiancarbide, tantalum carbide, tungsten carbide and zirconium carbide; andvarious metal silicides such as described in Silicides for VLSIApplications, S. P. Murarka (Academic Press, 1983), pp. 30-31. Theconductive core particle preferably has a somewhat rounded shape withfew if any sharp or highly angular surfaces. Approximately sphericalparticles are preferred.

Surprisingly and unexpectedly, the present inventors have discoveredthat applying a conductive ALD coating (or a semiconducting coating withan electronic band gap that is less than the operating voltage) to thesurface of a 3,000 nm base metal electrode powder (copper) that hadnative oxide remaining intact, resulted in non-conductive compositeparticles. This observed result is contrary to what is disclosed orimplied in the Weimer et al. Patent, which describes “a non-conductivecoating that is deposited on core conductive particles using atomiclayer deposition methods.” For example, one of the examples in theWeimer et al. Patent describes 5,000 nm diameter iron particles coatedwith 5.5 and 22 nm Al₂O₃ films. The Weimer et al. Patent also identifiedthe presence of an Fe₂O₃ native oxide interlayer (a commonly knowninsulator) at the interface between the innermost surface of the coatingand the outermost surface of the core particle. Elsewhere, Weimer et al.have published that 7.5 nm-22 nm coatings on micron-sized Nickel powderdemonstrated a similar nonlinear resistivity to the coated irondescribed in the Weimer et al. Patent. See, “Ultrafast metal-insulatorvaristors based on tunable Al₂O₃ tunnel junctions” Applied PhysicsLetters 92, (2008) 164101. However, no mention was made in this work asto whether the native oxide remained intact at the surface or ifpretreatment steps were utilized to remove the native oxide. The Weimeret al. Patent implies that the insulating Al₂O₃ coating is the exclusivefeature of their invention that provides non-linear resistivity withfilm thickness, while neglecting the contribution of the native oxide,which is also commonly known to be an insulator. There is an implicitpresumption that the uncoated core conductive particles used for thestudy were tested in the same manner as the coated particles, however nodata is presented for the 5,000 nm diameter iron particles with a nativeFe₂O₃ layer, nor is any particle size smaller than 5,000 nm described.More importantly, it is well known to those skilled in the art ofproducing electronic components from powdered materials or inkscontaining powdered materials that there is a strong non-linearresistivity with respect to pressure. The Weimer et al. Patent does notdiscuss pressure; the publication however offers that the materials wereplaced in a centrifuge, and it is implicitly understood to be subject toa very high compaction pressure. This matrix of particles produced andtested is entirely different from how conventional passive electronicscomponents such as conductors and capacitors are produced, specificallyusing an electrode layer produced through the printing of aparticle-containing ink. Most surprisingly to the inventors was thediscovery that conductive particles of 1,000 nm and smaller, firsthaving the native oxide removed, and second having a coating process inwhich a thin (typically 2-6 nm) insulating ALD film was applied, wasparticularly useful as a conductive electrode powder for passiveelectronics components consisting of layers of electrode powdersproduced using conventional ink printing technologies, and moreover thatthese materials could be drop-in replacements for conductive electrodepowders that did not have a thin film coating.

One difficulty faced when dealing with fine metal powders, especiallysubmicron powders, is their propensity to form native oxide films in thepresence of air and moisture, even at standard temperatures andpressures. For example, in the examples discussed above by Weimer etal., ALD-coated 5 micron metallic iron particles showed the presence ofiron oxide at the interface between the particle and coating. It is wellknown to one skilled in the art that steps to remove this native oxideprior to coating can significantly improve the quality of the coatedmetal powders and their suitability for use in particular applications.Processes for removing native oxides are well known to one skilled inthe art. For example, gas-solid contacting steps, in which metalparticles are exposed to reducing gases at elevated temperatures, areoftentimes suitable in reducing the oxidation state of core materials,promoting oxygen vacancies, and/or promoting other beneficial phenomena.Similar reducing gas (e.g., “forming gas”) exposures (sometimes referredto as protonation pretreatment steps) have been successful in improvingproperties of dielectric materials such as BaTiO₃. As is the case withpristine (i.e., substantially pure or a purity of at least 95%,typically at least 98% often at least 99%, and more of the at least99.5%) metals that have higher surface energy than their native oxidecoated counterparts, there is a strong likelihood that ultrafinemetallic particles will permanently sinter or otherwise agglomerate ifadjacent particles with reduced surfaces are allowed to come in contactwith one another for extended periods of time during reduction steps inelevated temperature. Coatings have proven to be useful in preventinginter-particle sintering. In general, coating can prevent sinteringentirely compared to uncoated particles that undergo sintering undersimilar conditions. In some instances, coating allowed a significantreduction in sintering as evidenced by requiring prolonged time and/orsintering temperature. In some cases, coating a particle increasedsintering temperature as much as 200° C. to 300° C. compared to uncoatedparticles under similar conditions.

Some aspects of the invention, therefore, provide a metallic particlecomprising a continuous nanoscale coated oxidation-resistant andelectric conducting film. In some embodiments, the coating is anultrathin coating consisting of a single to a plurality of atomic layercoatings. In one particular embodiment, the coating is an aluminum oxidecoating. The particle size of the metallic particle, prior to coating,is typically from about 50 nm to about 3,000 nm, often from about 80 nmto about 1,000 nm, and most often from about 100 nm to about 600 nm.Typically, the “base material” comprises nanoparticles. In someembodiments, the electrically-conductive particle described herein mayhave a median particle size of 3,000 nanometers or less, for examplefrom about 50 nm to about 3,000 nm, often from about 80 nm to about1,000 nm, and most often from about 100 nm to about 600 nm.

As stated above, compositions of the invention can be used in a widevariety of passive electronic components including in conductors,transducers, actuators, piezoelectrics, transistors, thyristors, andcapacitors. Methods and compositions of the invention can also be usedin conductor-coated metals as core-shell electrode powders. Providing acoating of thin film as described herein provides a wide variety ofbeneficial effects including, but not limited to, limiting agglomerationduring coating process and still achieve results, i.e., maintainsubstantially the similar electric conductivity and/or resistivity.Molecular layer deposition (MLD) process coated particles generally canbe calcined to allow the coating shells to become porous and allow forforming-gas reduction of metals while preventing metals from sintering,i.e., enabling native oxide removal without sintering. An exemplary MLDprocess includes the in situ production of these materials by coatingMLD films on metal oxalate particles, then decomposing the metal oxalateand making MLD porous in single process. Methods of the invention can beused to also produce core-shell magnetic materials, i.e., magneticnanoparticles that are coated with a thin film of non-magnetic “shell”.

Compositions of the invention can also be used to produce improvedelectrode layers by printing, spraying or other means to achieveultrathin layers for MLCCs, single-layer capacitors, batteries,ultra-capacitors, etc. For example, compositions of the invention can beused to emulate a “three dimensional current collector” which isutilized in lithium ion batteries to reduce the thickness of the foilsof the cells, and/or reduce the amount of certain conductive additivespecies, and/or increase the internal electrical conductivity ofelectrodes and consequently allow for thicker electrodes andsubstantially increase the energy density of batteries or allow for thebattery to be extremely compact. Using the compositions of the inventionto produce a three dimensional structure or network of highly conductiveelectrical pathways can allow for thicker active energy storage devicecomponents such as electrodes, and enable thinner, lower cost passiveenergy storage device components such as current collectors, separators,and other ion channels. The protective features of the ALD coatings canbe used for high conductivity metallic or polymeric materials, orconventional carbon-based conductive materials or additives, impartingsimilar interfacial stabilization benefits without adversely impactingthe role of function of the substrates in the device. Since batteryelectrodes require electronic conductivity to effectively stimulate thetransport of electrochemically active ions throughout an electrodethickness, an object of the invention is to allow for thicker electrodes(thereby increasing energy density) to be produced without sacrificingthe electrical network. In this manner, an electrode with, for example,a 90% active material loading, can be processed at 2× the conventionalthickness and achieve the same lifetime as the baseline electrode of theconventional thickness. The alternative method of increasing energydensity is to increase the active loading from 90% to 95%, 96%, 97%, 98%and sometimes 98.5%, by reducing the amount of binder and conductiveadditive. In some circumstances an electrically-conductive secondaryphase with binder-like properties can be applied to the surfaces of theactive materials, in such a way that the coated active materialscomprise 100% of the electrode. However, generally, at some point acritical maximum electrode thickness is typically reached for eachactive material loading increase, which shrinks with reduced conductiveadditive. The ALD-coated conductive particles used in this inventionallow for an increase in energy density of a finished battery by 10%,oftentimes 25%, sometimes 35%, and occasionally 50%, depending on theparticular design of the electrodes and cells, as well as the selectionof the active and passive material components.

In one aspect, provided is an electrode layer for an energy storagedevice which includes active and passive components. The electrode layerincludes passive, electrically-conductive particles coated with a thinfilm of protective material. In at least one embodiment, the function ofthe said electrode layer is substantially the same to a similarelectrode layer of passive, electrically-conductive particles in theabsence of the protective material.

Suitable passive, electrically-conductive particles may include metallicor polymeric materials. Exemplary metallic and/or polymeric materialsinclude, but are not limited to aluminum, platinum, silver, gold,titanium, copper, zinc, chromium, nickel, iron, molybdenum, tungsten,ruthenium, palladium, indium, PtNi, FeCrAlY, AgPd, nichrome, otherconductive steels, PEDOT, carbons, carbon black, acetylene black,activated carbon, carbon nanotubes, carbon fibers, vapor grown carbonfibers, carbon nanoribbons, graphite, graphene, diamond or diamond likecarbon, and other conductive polymers, and the like or combinationsthereof. In at least one embodiment, the passive,electrically-conductive particles include carbons, graphite, graphene,diamond or diamond like carbon.

Suitable methods for depositing the thin film on theelectrically-conductive particles or for producing the thin film aredescribed herein. Such methods may include, but are not limited to,atomic layer deposition, molecular layer deposition, chemical vapordeposition, or combinations thereof. The electrode layer may be suitablyproduced from a casting, printing or spraying process.

In another aspect, provided is an energy storage device which includesan electrode layer having passive, electrically-conductive particles, asdescribed herein. The electrically-conductive particles may include oneor more of copper, nickel or aluminum, and may be coated with one ormore thin film protective materials. The coating may be produced usingmethods described herein such as the atomic layer deposition or themolecular layer deposition process.

In yet another aspect, provided is an energy storage device whichincludes an electrode layer having one or more passive,electrically-conductive coatings having a resistivity value less than10,000 μΩ-cm, produced using atomic layer deposition or molecular layerdeposition.

As used herein, the term “improved” with respect to life-time refers tohaving increased life-time of the passive electronic components due tothe coating of thin film on nanoparticles or thin film onelectrically-conductive particles. Typically, the life-time of anelectrode layer comprising coated particles according to the presenttechnology is increased by at least 10% more, typically at least 25%more, and often at least 50% more, compared to an electrode layer withthe similar (i.e., uncoated) particles. Alternatively, “improved” withrespect to rate capability can refer to having an increased ratecapability, as defined by the ratio between the achievable capacityduring a 6C (10 minute) charging or discharging step, versus a 1C (1hour) charging or discharging step, where the rate capability of anelectrode layer comprising coated particles is at least 10% more,typically at least 25% more, and often at least 50% more, compared to anelectrode layer with the similar (i.e., uncoated) particles or one thatuses conventional carbon-based conductive particles alone. Sometimes therate capability ratio can be defined as the 1C rate capacity divided bythe 0.1C, 0.5C or 0.2C rate capacity; other times the rate capabilityratio can be defined as the 2C, 3C or 4C rate capacity divided by the 1Crate capacity. In all cases, the rate capability will be a percentagebetween 0 and 100%, and an improved rate capability will be signified bya percentage that is larger than its baseline percentage.

Some compositions of the invention include ceramic-coated dielectricparticles. Typically, the atomic layer deposition (ALD) process is usedto produce core-shell dielectrics. As used herein, unless the contextrequires otherwise the term “core” refers to the nanoparticles and theterm “shell” refers to the thin film coating on the nanoparticles. Insome cases, the presence of thin film coating improves or prevents ionmobility in dielectric nanoparticles. In other instances, the thin filmcoating can be used to manipulate or affect the final particle size,e.g., after firing or heating.

Some compositions of the invention include conductive ALD coatingsapplied directly onto the active material components of an energystorage device. In these compositions as they pertain to batteries, ALDis used to deposit a conductive coating (films or nanoparticles) aroundcathode and/or anode particles, which can achieve two goals: reduce orremove the need for a separate/discrete phase of conductive additiveparticles, and reduce the required thickness of, or in extreme casesremove the need for, a foil current collector, a binder or a conductiveadditive. An exemplary cathode material may include a lithium nickelmanganese cobalt oxide, coated with, amongst other potential materials,nanoparticles of a conductive metal that can reduce the amount ofseparate conductive additive required, and/or a conductive polymericcoating that can reduce the amount of separate binder required toachieve/maintain a proper level of adhesion between the electrode andthe current collector. In these cases, the ALD coatings may have abifunctional effect of providing a stabilizing effect or improving thesafety of the active materials independent of electrode design, whileenabling an electrode design that is substantially thicker withoutadversely affecting the already provided stability and safety effect.The net result is that the electrode thickness can be increased(increasing energy density), the active material content can beincreased (increasing energy density), and current collector thicknessescan be decreased (increasing energy density and reducing costs). Withthe full adoption of the envisaged solutions within both cathode andanode, may allow for an increase in energy density of a finished batteryby 20%, oftentimes 45%, sometimes 65%, and occasionally 80%, dependingon the particular design of the electrodes and cells, as well as theselection of the active and passive material components.

A thin film coating present on the nanoparticles of the inventionprevents sintering at high temperature, e.g., during forming gasreduction process. In some cases, the thin film coating, e.g., SiO₂coating, is thin enough to be permeable to reducing gas such as hydrogenwhile preventing sintering of nanoparticles. In some instances,compositions of the invention include MLD-coated particles where thethin film coatings become porous ceramic oxides to allow gas flow. Insuch instances, a second coating of thin film can be applied, e.g.,after heat treatment. In other instances, the second coating of thinfilm provides an impermeable dielectric layer.

The thin film of coating can be applied to nanoparticles using a batchprocess (see the Weimer et al. Patent), a semi-continuous process (seecommonly assigned U.S. patent application Ser. No. 13/069,452, entitled“Semi-Continuous Vapor Deposition Process For The Manufacture of CoatedParticles”), a continuous process (U.S. Patent Application PublicationNo. 20120009343), as well as variations thereof includingplasma-enhanced processes, or a combination thereof.

Additional objects, advantages, and novel features of this inventionwill become apparent to those skilled in the art upon examination of thefollowing examples thereof, which are not intended to be limiting. Inthe Examples, procedures that are constructively reduced to practice aredescribed in the present tense, and procedures that have been carriedout in the laboratory are set forth in the past tense.

Examples

Example 1: Metallic copper particles devoid of native copper oxidecoating, with and without ALD encapsulation coatings, have been producedin a set of six trials, using two different copper substrates to compareand contrast coating processes: two trials utilized 1-5 micron copperpowders that maintained a nanoscale native oxide of copper in theas-received state (substrate A); and two trials utilized thedecomposition of a copper oxalate powder in a fluidized bed reactor(substrate B). For substrates A and B, the following processes were run:

-   -   (1) Forming gas exposure at elevated temperature (450° C.) for        60 minutes;    -   (2) The process of (1) followed by a 3 nm ALD coating of Al₂O₃;        and    -   (3) A first coating of a 5 nm aluminum alkoxide layer via the        Molecular Layer Deposition (MLD), which results in a mesoporous        Al₂O₃ coating during an elevated temperature organic burn-out        step. Subsequently the process of (2) was followed, inclusive of        the process of (1) as described above.        For cases A-1 and B-1, particle size distributions were shifted        to dramatically larger values, a clear indication that        inter-particle sintering was rampant. The d50 particle size        using the B substrate is typically smaller than the d50 particle        size of a bulk micron-scale powder of the same metal. After        being exposed to air for 24 hours, copper oxide was clearly        observed using XRD. For cases A-2 and B-2, a similar shift in        particle size occurred, as that aspect of the processing was        identical, however the Al₂O₃ coatings prevented the oxidation of        the underlying copper powders as copper oxide was not observed        using XRD. For cases A-3 and B-3, the aluminum alkoxide converts        to a porous Al₂O₃ shell during the forming gas treatment step,        which allows for forming gas to directly contact the surface of        the particles, and the reduction step can proceed to completion        while only the outermost Al₂O₃ surfaces are in contact with one        another within the particle bed. Upon completion of the forming        gas reduction step, the Al₂O₃ ALD shell was applied. The 3 nm        Al₂O₃ ALD coating was again sufficient to prevent the oxidation        of copper particles upon exposure to air for 24 hours. The        dramatic difference between A-3 and B-3, relative to the        analogues seeing only processes 1 and 2, was that the particle        size remained largely unchanged, aside from what is naturally        expected when carrying out such intensive, sequential coating        processes on particles in vacuum fluidized bed reactors with        vastly different temperature processing steps.

Example 2: Barium titanate particles with and without ALD coatings weresubject to protonation steps, or high temperature forming gas exposures.Uncoated barium titanate treated for 1 hour at 900° C. in forming gas(4% H₂ in N₂), produced a locally-sintered powder with particle sizedistribution shifted to significantly larger sizes. Al₂O₃ and SiO₂ ALDcoatings were applied to pristine barium titanate particles as well, andin both cases after identical forming gas treatments, the nanoscalecoatings were sufficient to prevent sintering-induced aggregationobserved extensively with the uncoated materials. The Al₂O₃-coatedbarium titanate turned a deep blue color, perhaps evidence that aluminumdoping and/or barium aluminate formation occurred. However with theglassy SiO₂ coating, the material turned dark gray only, whilemaintaining a uniform particle size distribution that was changed onlydue to the fluidized bed coating process itself. This set of coatingtrials elucidated the value of tailoring the sintering preventioncoating for specific processes, in that hydrogen gas in the forming gasprocess could much more readily diffuse through the deposited SiO₂ ALDcoatings than the deposited Al₂O₃ ALD coatings, while the effect ofsintering prevention was maintained independent of these coatingmaterials. The protonated SiO₂-coated barium titanate can then beovercoated using protective Al₂O₃ layers for a grain boundary barriereffect, additional SiO₂, Li₂O or B₂O₃, layers to serve as frittingmaterial, or other coatings depending on the desired purpose.

Example 3: ALD-coated submicron-sized nickel powders have beenformulated into standard inks for producing MLCC inner electrode tapes,alongside tapes made from inks formulated using uncoated nickel powders.Prior to this formulation, it is advantageous to better understand anddefine the minimum critical coating thickness required to prevent basemetal oxidation during the binder burnout process. This process istypically run at no higher than 270° C. for 12 hours in air; however itis highly desirable to increase the working temperature to 300° C. for12 hours in air to reduce the residual carbon and impurities that arenormally left behind after an incomplete binder burnout process at lowertemperatures. The Ni and NiO content was measured on raw powders beforeand after this thermal treatment step in a standard tube furnace. Thecontrol sample prior to the binder burnout process had a NiO content of0.1 wt % as measured using powder XRD. The heat treated control samplehad a resulting NiO content of 16.6%; one heat treated ALD-coated samplethat was coated below the critical thickness had a resulting NiO contentof 10.5%. Thicker ALD-coated samples at or above the critical thicknesshad resulting NiO contents of 0.2% or 0.1%.

Example 4: The alkali niobate/nickel co-fired MLCC system is one of aselect number of possible candidates for lead-free high temperature,high voltage, high reliability capacitors for high temperature powerelectronics (e.g., SiC-based ICs) that require 150° C.-300° C. deviceoperation. Another such candidate is bismuth zinc titanate-bariumtitanate (BZT-BT) dielectric layers ideally paired withoxidation-resistant copper inner electrodes. MLCCs consisting of layersof coated (at the defined critical thickness) vs. uncoated inner(nickel) electrode tapes and tapes made from formulated pristine alkaliniobate powders were each fabricated to test the hypothesis thatpassivated base metal electrodes could be used as drop-in replacementsto pristine nickel powders for MLCC applications. Post binder burnout,it is common to vary the oxygen partial pressure during high temperatureco-firing steps and measure the dielectric constant and dielectric loss(tan δ) of the system to optimize the co-firing process for any newmaterials. For a given cast tape thickness, the optimal results would bea controllable dielectric constant for the layer, and minimal loss.

Processes and procedures to modify or tailor the dielectric materials inthe dielectric layer have demonstrated control over these variables, sothe anticipated result of utilizing passivated Ni tapes relative topristine tapes was that the dielectric properties of the system would beunchanged, but perhaps a higher voltage bias would be needed to utilizethe capacitor devices if the teachings of nonlinear resistivity byWeimer et al. were accurate in submicron base metals and sub 5 nmcoating thicknesses. Two unexpected results were demonstrated by thistest. First, the use of passivated inner electrodes did not requirealtering the electrical test conditions, likely suggesting thatparticles smaller than 1 micron in diameter and/or films thinner than 5nm may not have been produced and evaluated by Weimer. Second, the useof ALD-coated inner electrode materials delivered a significant degreeof robustness to the entire system with respect to a highly uniform andconsistent dielectric constant with respect to co-firing oxygen partialpressure, and an incredibly low dielectric loss. This is the firstdemonstration of coated inner electrode materials paired with pristinedielectric materials that has delivered some of the same benefits asmodifications to the dielectric materials themselves. The implicationsof this are broad and far-reaching, in that not only can ALD-coatedinner electrodes be used to withstand operating conditions of nextgeneration high temperature integrated circuit devices, but thatrelatively simple and low-cost metal coating steps can supplant theextensive and oftentimes complicated dielectric modification stepsdescribed herein. In addition, with better control over the dielectricproperties of individual layers, the practical number of layers withinALD-incorporated MLCCs should be significantly larger than without usingALD-coated materials. This has a direct impact on the energy densityattainable in MLCC devices.

The alkali niobate/nickel co-fired MLCC system was tested using tinoxide coated Ni to determine whether an insulator-metal compositeparticle was critical to affecting the dielectric properties of thesystem, or if a conductive coating could yield the same unexpectedresults. Other materials have also been coated on Ni, such as SiO₂,B₂O₃, TiO₂, Ta₂O₅, Si₃N₄, TiN and other metal oxides and nitridescommonly known to be applied using ALD techniques.

In order to further optimize the systems toward high temperaturelead-free capacitors for demanding applications (e.g., DC Linkcapacitors), the previously described BZT-BT/Nickel and BZT-BT/Copperco-fired MLCC systems were tested with coated and uncoated electrodepowders, and some variants included coatings and/or pretreatments to thedielectric materials themselves. Glassy coatings including SiO₂ and B₂O₃may also be useful to improving the overall homogeneity of theseco-fired systems.

Standard barium titanate/Ni co-fired MLCC systems were also tested withcoated and uncoated electrode powders, and some variants includedcoatings and/or pretreatments to the dielectric materials themselves.Glassy coatings including SiO₂ and B₂O₃ were useful to improving theoverall homogeneity of these co-fired systems.

Example 5: Plasma-enhanced atomic layer deposition (PE-ALD) coatingtechniques are commonly used to remove residual contaminants fromincomplete surface reactions at lower operating temperatures. A PE-ALDTiN coated Ni electrode tape was produced along with a conventionallyproduced ALD TiN coated Ni electrode tape, to determine whether a changein residual contaminant (typically Cl from TiCl₄) level results in ahigher electrical conductivity in a particle system, and whether thiswould affect the dielectric constant and loss to as great of a degree asan insulative coating or a less conductive coating. An exemplarydemonstration is the production of TiN ALD coatings on particles, inwhich TiCl₄ and NH₃ can be administered in sequential fashion with HClbeing the reaction product. Even at 400° C., there can be residualchlorine in the coatings, which makes the coatings materially differentfrom TiN coatings devoid of contaminants. The TiN process for coatingparticles is identical to that demonstrated by Lakomaa in 1992 for TiO₂(see “Atomic layer growth of TiO₂ on silica”, Applied Surface Science60/61 (1992) 742-748), except NH₃ replaces H₂O in sequentialself-limiting gas-solid contacting steps on particle surfaces in the bedof powder. Low temperature ALD processes using TiCl₄ and H₂O can leave2.0-10.0 wt % chlorine in the films. More recently, Elam et al.(“Surface chemistry and film growth during TiN atomic layer depositionusing TDMAT and NH₃ ” Thin Solid Films 436 (2003) 145-156) disclosed aroute to TiN ALD using tetrakis-dimethylamino titanium and ammonia, andeven this precursor resulted in 2-5 wt % carbon in the film. The bestfilms possessed a resistivity more than 600 times that of bulk TiN,which is unappealing for most conductive coating applications. TiN viathermal ALD typically has resistivity values >10,000 μΩ-cm, whereasPlasma-Enhanced TiN ALD typically has resistivity values <300 μΩ-cm.PE-ALD was used to deposit TiN onto Ni powders, which are then used asinner electrodes in MLCCs.

The surprising and unexpected discovery of the effect that co-firedALD-coated inner electrodes have on MLCC devices is especially useful ifthe materials can be coated economically and at industrially-relevantrates. The submicron-sized Ni power described earlier was loaded into asemi-continuous ALD reactor as described by commonly assigned U.S.Patent Application Publication No. 2011/0236575, and passed through thesystem at high rates to determine the feasibility of mass production.The core material was passed through the semi-continuous counter-currentflow system for the appropriate number of times to achieve thepreviously defined critical coating thickness for the material. Theoxidation resistance of this material was identical to that produced inlab-scale fluidized bed reactors, however the throughput in thesemi-continuous ALD reactor is ˜200 times the throughput of batchsystems, yet maintains a nearly equivalent footprint. These tests atboth the small scale and large scale demonstrate the applicability ofproducing the composite materials in a large scale, and the ability toincorporate these compositions into conventional and high temperatureMLCC devices, and applicability to a wide array of electronic componentsand devices that are fabricated using inks, pastes or tapes that includeoxidation-resistant base metal electrode powders.

Example 6: The coated metallic copper particles of Substrate A andSubstrate B produced in Example 1 were evaluated for suitability as aconductive additive into a battery electrode. Copper particles (1-5micron and nano-sized) were coated using an atomic layer depositionprocess, where the coatings were confirmed to increase the oxidationonset temperature of each powder by at least 25° C. The powders werepre-blended with graphite powder and loaded into a slurry containingPVDF and NMP solvent, at a ratio of 90:5:5 and 80:15:5 for comparativeevaluations (Graphite:Copper:PVDF), while baseline electrodes wereproduced using the same ratios, but using an uncoated carbon-basedconductive additive in place of the copper. Each slurry was cast onto acopper current collector, at 10 mg/cm² and 20 mg/cm², in order todemonstrate the ability for the electrodes that incorporated the coatedconductive metal particles to have longer life, especially with thickerelectrode layers. Anode electrodes were paired with balanced NMC-basedcathode electrodes at similar active loading amounts, using an uncoatedcarbon-based conductive additive. The 3-D current collector network ofinternal electrode powders was evaluated using charge-discharge cyclingand impedance measurements before coating and after every 8charge-discharge cycles.

The results of the anode trials are shown in Table 1, for the twodifferent levels of additive loadings:

TABLE 1 Results of 3-D current collector network comprising copper forLi-ion battery anodes 5% Additive 15% Additive (90% Active, 5% PVDF)(80% Active, 5% PVDF) Pristine Pristine ALD Pristine Pristine ALD MetricCarbon Copper Copper Carbon Copper Copper Init. 1 C Cap. (mAh/g) 208.1210.1 210.0 183.9 185.1 184.9 Coulombic Efficiency 87.2% 88.9% 88.7%87.1% 88.8% 88.9% Delta Impedance: +15.8 −7.0 −6.8 +13.1 −9.3 −8.8 24cycles (ohms) Cycle Life 142 51 174 181 37 226 6 C Cap/1 C Cap 68% 92%88% 76% 91% 93%

Example 7: Coated metallic aluminum particles were evaluated forsuitability as a conductive additive into a lithium-ion battery cathode.Aluminum particles (1-5 micron and nano-sized) were coated using anatomic layer deposition process, where the coatings were confirmed toincrease the oxidation onset temperature of each powder by at least 25°C. The powders were pre-blended with a lithium nickel manganese cobaltoxide (NMC) powder and loaded into a slurry containing PVDF and NMPsolvent, at a ratio of 90:5:5 and 80:15:5 for comparative evaluations(NMC:Aluminum:PVDF), while baseline electrodes were produced using thesame ratios, but using an uncoated carbon-based conductive additive inplace of the aluminum. Each slurry was cast onto an aluminum currentcollector, at 10 mg/cm² and 20 mg/cm², in order to demonstrate theability for the electrodes that incorporated the coated conductive metalparticles to have longer life, especially with thicker electrode layers.Cathode electrodes were paired with balanced graphite-based cathodeelectrodes at similar active loading amounts, using an uncoatedcarbon-based conductive additive. The 3-D current collector network ofinternal electrode powders was evaluated using charge-discharge cyclingand impedance measurements before coating and after every 8charge-discharge cycles. A similar effect on impedance was observed forthe 3-D current collector for cathodes as was demonstrated in Table 1for anodes. The first-cycle capacity was 1.5% and 1.6% higher for theuncoated aluminum and ALD-coated aluminum comprising cathodes,respectively, relative to the uncoated carbon-based additive baseline.For these samples, there was no substantial benefit or detriment to fastcharge capability (as measured by 6C versus 1C charge rates), whichsuggests that the limitation to fast charging was within the anode forthese particular electrodes.

Example 8: The coated metallic copper particles of Examples 1 and 6 wereagain deployed to fabricate an anode incorporating a powder-based 3-Dcurrent collector. In this trial, a bi-layer anode was produced toemulate a conductive additive gradient anode, wherein a layer comprisinga conventional carbon-based conductive additive is positioned adjacentto the separator, and a layer comprising an ALD-coated copper-basedconductive additive is positioned adjacent to the copper currentcollector. The powders were each pre-blended with graphite powder andloaded into a slurry containing PVDF and NMP solvent, at a ratio of90:5:5 (Graphite:Copper:PVDF). First, the slurry comprising the copperadditive was cast onto a copper current collector, at ˜10 mg/cm² andallowed to dry in an inert environment overnight. Second, a slurrycomprising the carbon-based additive was cast onto the dried copperadditive-containing electrode also at a loading of ˜10 mg/cm², in orderto emulate a thicker electrode with a network of conductive additivesthat transitions from copper toward the copper current collector side,and conventional graphite toward the separator. Cathode electrodes werepaired with balanced NMC-based cathode electrodes at similar activeloading amounts (for the combined ˜20 mg/cm² loading), using an uncoatedcarbon-based conductive additive. The 3-D current collector network ofinternal electrode powders was evaluated using charge-discharge cyclingand impedance measurements before coating and after every 8charge-discharge cycles. Interestingly enough, the measured 6C/1C ratio(one measurement of rate capability) for the ˜20 mg/cm² loading of thebi-layer anode was within the experimental error to the rate capabilityfor the ˜10 mg/cm² baseline anode (that included a carbon-basedconductive additive alone). These results suggest that the incorporationof an ALD-coated metallic powder can be an effective way to increase therate capability of thickly-casted battery electrodes, while protectingthe surfaces of these metals becomes increasingly important formaterials positioned closer to the center of the battery (versus theextremes where the metallic current collector is already located. Theseresults also emulate the potential benefits of using a coated currentcollector versus an uncoated current collector.

Example 9: The PE-ALD TiN process described in Example 5 is applied tolithium nickel manganese cobalt oxide (NMC) powders used as cathodematerials, and natural graphite powders used as anode materials, inlithium ion batteries. The purpose of the coatings is to produce anelectrically-conductive ceramic coating that acts as thethree-dimensional current collector of the invention as applied toenergy storage devices and batteries. Various coating thicknesses from0.5 nm to 20 nm are applied to powder surfaces in a reactor configuredfor atomic layer deposition coatings described above. Of particularimportance is the plasma-effect, which provides for highly conductivecoatings on substrate interfaces, and minimizing the total mass requiredto be applied to overcome the localized percolation threshold forenhanced conductivity. ALD coatings of 1-5 nanometers applied to NMCpowders and 2-10 nanometers applied to graphite powders, allow forincreased electrode thicknesses by 15-40% for cathode electrodes, and35-75% for anode electrodes, respectively.

Example 10: A copper ALD process, based upon an amidinate precursor, isapplied to natural graphite powders used as anode materials in lithiumion batteries. The purpose of the coatings is similar to what isachieved in Example 9, to produce an electrically-conductivenanoparticulate metallic coating that acts as the three-dimensionalcurrent collector of the invention as applied to energy storage devicesand batteries. Various coating thicknesses from 0.5 nm to 10 nm areapplied to powder surfaces in a reactor configured for atomic layerdeposition coatings described above. It has found that since the ALDcopper alone can sometimes behave similarly (in certain electrodedesigns) to the uncoated copper loaded into the anode electrode inExample 6, a TiN ALD process applied in Example 9 can be furtherdeployed as a copper ALD stabilization coating (0.5 to 2.5 nanometers issufficient). A composite electrode comprising 96-98% active materialcoated with a first layer of copper and a second layer of TiN (remainderPVDF binder) can achieve a similar lifetime as an electrode comprising90% active material, 5% conductive carbon additive and 5% PVDF binder.

Example 11: A copper ALD process, based upon an amidinate precursor, isagain applied to natural graphite powders used as anode materials inlithium ion batteries. However instead of a conductive ceramic TiN ALDcoating, the conductive polymer PEDOT is applied to the copper ALDcoated active materials. PEDOT coatings ranging from 3 nm to 35 nm areapplied to Cu-coated graphite particles (with and without TiN ALDcoatings), and assembled into electrodes that comprise 100% coatedgraphite particles—i.e. no separate conductive additive and no separatebinder material. The energy density of these electrodes surpasses theattainable energy density of conventional electrodes by providing forthe elimination of all non-active material phases within the electrodelayer.

The foregoing discussion of the invention has been presented forpurposes of illustration and description. The foregoing is not intendedto limit the invention to the form or forms disclosed herein. Althoughthe description of the invention has included description of one or moreembodiments and certain variations and modifications, other variationsand modifications are within the scope of the invention, e.g., as may bewithin the skill and knowledge of those in the art, after understandingthe present disclosure. It is intended to obtain rights which includealternative embodiments to the extent permitted, including alternate,interchangeable and/or equivalent structures, functions, ranges or stepsto those claimed, whether or not such alternate, interchangeable and/orequivalent structures, functions, ranges or steps are disclosed herein,and without intending to publicly dedicate any patentable subjectmatter. All references cited herein are incorporated by reference intheir entirety.

1-27. (canceled)
 28. A method of making a dielectric or piezoelectriccomponent, comprising: providing nanoparticles comprising an alkaliniobate perovskite; coating the nanoparticles with an alkali tantalateto form coated nanoparticles; and firing the coated nanoparticles toform the dense component.
 29. The method of claim 28 wherein the coatingof alkali tantalite is applied by ALD or MLD in a fluidized bed reactor.30. The method of claim 29 wherein the 80% or more of the nanoparticleshave a particle size of 1000 nm or less, and wherein the coating has amean or medium thickness of about 20 nm or less, or 2 nm to 6 nm. 31.The method of claim 30 wherein the dense component has an average grainsize that is at least 20 nm smaller than a component made under the sameconditions but with uncoated nanoparticles.
 32. The method of claim 30wherein the nanoparticles were reacted with a reducing gas prior to thestep of coating.
 33. (canceled)
 34. A MLCC comprising a layer formed bythe method of claim
 28. 35. A method of forming Ni powders, comprising:treating Ni powders with a reducing gas to remove surface oxide; andcoating the particles with alumina by ALD to form an alumina layerhaving a thickness of 2 to 6 nm.
 36. The method of claim 35 furthercomprising a first step of coating the particles with a porous layer ofAl₂O₃.
 37. The method of claim 36 with the porous layer of Al₂O₃ isformed from aluminum alkoxide followed by an ALD coating of Al₂O₃. 38.The method of claim 35 wherein the 80% or more of the particles have aparticle size of 1000 nm or less.
 39. A component formed by the methodof claim
 35. 40. The component of claim 38 wherein the powder is Nipowder and wherein the component comprises 0.2 wt % or less NiO.
 41. AMLCC comprising the component of claim
 40. 42. A method of forming Cupowders, comprising: treating Cu powders with a reducing gas to removesurface oxide; and coating the particles with alumina by ALD to form analumina layer having a thickness of 2 to 6 nm.
 43. The method of claim42 further comprising a first step of coating the particles with aporous layer of Al₂O₃.
 44. The method of claim 43 with the porous layerof Al₂O₃ is formed from aluminum alkoxide followed by an ALD coating ofAl₂O₃.
 45. The method of claim 42 wherein the 80% or more of theparticles have a particle size of 1000 nm or less.
 46. A componentformed by the method of claim
 42. 47. The component of claim 46 whereinthe powder is Ni powder and wherein the component comprises 0.2 wt % orless NiO.
 48. A MLCC comprising the component of claim
 47. 49-52.(canceled)